The present invention relates to a computer system in which a computer is divided into a plurality of logical computers which constitute a logical parallel computer, and more particularly to data transfer between logical computers.
A parallel computer constituted of one or more processing units and a coupling unit shared by the processing units is disclosed in U.S. Pat. No. 5,561,809.
According to this disclosure, data write from each processing units (central processing complex: CPC) to a shared unit (structured-external-storage facility: SES facility) is performed in the following manner. First a processing unit stores data in its message buffer and transmits a write command to the coupling unit. Thereafter, the data stored in the message buffer of the processing unit is transferred to a message buffer of the coupling unit. Upon reception of the write command sent from the processing unit, the coupling unit analyzes the received command and transfers the data from the message buffer of the coupling unit to its memory. Lastly, the coupling unit returns a command processing result back to the processing unit.
When the processing unit reads data from the shared unit (SES facility), the processing unit transfers a read command to the coupling unit. Upon reception of the read command sent from the processing unit, the coupling unit analyzes the read command. The coupling unit transfers the data requested by the read command from a memory of the coupling unit to its message buffer, and transfers the data stored in its message buffer to a message buffer of the processing unit. Lastly, the coupling unit returns the command processing result and the message buffer storing the read result, back to the processing unit.
With the above method, during processing a command to be transferred from a processing unit to a coupling unit, data itself, or the body of data is transferred.